Temperature sensors for detecting temperature of exhaust gas from internal combustion engines have been used, and gas sensors for detecting the concentration of a particular component (such as oxygen) in the exhaust gas have also been used. A threaded portion is provided externally of each sensor, and the sensor is mounted to a mount body (such as an exhaust pipe) by screwing the threaded portion into a mounting hole of the mount body.
Generally, to mount a sensor to an exhaust pipe, the sensor is first mounted to the exhaust pipe, and then a connector connected to lead wires extending from the sensor is connected to a connector of, for example, an external circuit. However, when the sensor is integrated with the external circuit with no connector or when the connector is fixed before the sensor is fixed, the external circuit and/or the lead wires must be rotated together with the sensor when the sensor is screwed into the mounting hole, and difficulty arises in mounting the sensor.
In view of the above difficulty, a technique is disclosed in which a tubular rotary member (mounting member) having a threaded portion formed on its outer surface is disposed so as to surround a rib (housing) holding a sensor such that the rotary member is rotatable with respect to the rib (see Patent Document 1). With this technique, even when the sensor is integrated with an external circuit, it is not necessary to rotate the external circuit together with the sensor when the sensor is screwed into a mounting hole.
In the technique disclosed in Patent Document 1, an outward tapered surface is provided on a rearward-facing surface of the rib, and a corner portion is provided on a forward-facing surface of the rotary member and is brought into contact with the tapered surface to form a seal. In this case, the tapered surface allows the corner portion and thus the rotary member to expand radially outward. Therefore, the threaded portion on the outer surface of the rotary member is also expanded radially outward and is tightly engaged with a female threaded portion of the mount body, so that the threaded portion is unlikely to be loosened.